The field of invention is pyrotechnics, and more specifically powdered metal alloys or compounds used as pyrotechnic fuel.
Pyrotechnic devices of various kinds, such as automotive airbag initiators, are commonly used in many applications. Such devices contain pyrotechnic fuel, which ignites and bums when combined with an oxidizer and exposed to an igniting force such as heat or an electric current, generating a burst of high pressure which in turn is converted to useful work of some kind. It is also known to use a pyrotechnic booster in conjunction with a primary pyrotechnic device, such that the pressure and/or heat released by the ignition of the primary pyrotechnic device in turn ignites the pyrotechnic booster.
Ultra-fine powders of elemental metals, such as aluminum, zirconium, or titanium, have been used as pyrotechnic fuels in primary pyrotechnic devices. These powders have a low ignition sensitivity threshold. That threshold is the amount of energy required to ignite a pyrotechnic material, usually measured in joules. Elemental metal fuels typically have an ignition sensitivity threshold on the order of magnitude of microjoules, so they require very little energy to ignite. Elemental metal fuels ignite rapidly upon reaching their ignition sensitivity threshold, then burn rapidly thereafter. Thus, they are desirable for use in applications where rapid ignition and burning are required. However, this low ignition sensitivity threshold means that these powdered elemental metals must be handled very carefully during manufacturing to prevent accidental ignition. Additionally, the ignition sensitivity threshold of powdered elemental metal fuels decreases as the average particle size of the powder grows smaller, necessitating even greater precautions in handling.
Such elemental fuels have also been used in the past in pyrotechnic boosters, with the same drawbacks. Additionally, hydrated compounds such as titanium hydride (TiH.sub.2) and zirconium hydride (ZrH.sub.2) have been used in pyrotechnic boosters. As with the elemental metal fuels, though, these hydrated compounds possess low ignition sensitivity thresholds.